Integrated hydrogen production and carbon dioxide recovery process

Abstract

Integrated processes for hydrogen production and carbon dioxide recovery are described. The processes use a chilling stream in a cryogenic carbon dioxide recovery unit. The chilling stream chills a working fluid which chills the hydrogen-depleted tail gas stream from a hydrogen pressure swing adsorption (PSA) unit to form a carbon dioxide product stream.

What is claimed is: 
     
         1 . An integrated process for hydrogen production and carbon dioxide recovery comprising:
 introducing a feed stream comprising hydrocarbons or a carbonaceous feedstock to a synthesis gas production zone comprising a syngas reactor to produce a synthesis gas stream comprising hydrogen, carbon dioxide, carbon monoxide, and methane;   separating the synthesis gas stream in a hydrogen pressure swing adsorption (PSA) unit to form a high-pressure hydrogen product stream enriched in hydrogen and a hydrogen-depleted tail gas stream;   chilling a working fluid stream with a chilling stream in a first heat exchanger forming a chilled working fluid stream and a warmed chilling stream;   chilling the hydrogen-depleted tail gas stream with the chilled working fluid stream in a main heat exchanger in a cryogenic carbon dioxide separation unit forming a chilled dried hydrogen-depleted tail gas stream and a warmed working fluid stream, and separating the chilled hydrogen-depleted tail gas stream into a carbon dioxide product stream comprising carbon dioxide, and an overhead stream; and   passing the warmed working fluid stream to the first heat exchanger.   
     
     
         2 . The process of  claim 1  wherein the chilling stream comprises liquefied natural gas, or liquid nitrogen, or liquid ammonia, or liquid hydrogen, or combinations thereof. 
     
     
         3 . The process of  claim 1  wherein the working fluid stream comprises a hydrofluoroolefin, a hydrocarbon having 1 to 5 carbon atoms, or combinations thereof. 
     
     
         4 . The process of  claim 1  further comprising:
 separating the overhead stream in an overhead separation unit to form a low-pressure carbon dioxide stream enriched in carbon dioxide and an off-gas stream enriched in hydrogen and at least one of carbon monoxide and methane; and 
 optionally recycling the low-pressure carbon dioxide stream to the cryogenic carbon dioxide separation unit. 
 
     
     
         5 . The process of  claim 4  further comprising:
 separating the off-gas stream in a second overhead separation unit to form a second hydrogen product stream and a second off-gas stream enriched in at least one of carbon monoxide and methane. 
 
     
     
         6 . The process of  claim 5  further comprising:
 passing the second off-gas stream to the synthesis gas production zone. 
 
     
     
         7 . The process of  claim 5  further comprising:
 passing at least a portion of the second hydrogen product stream to a process unit as fuel gas. 
 
     
     
         8 . The process of  claim 1  wherein separating the synthesis gas in the hydrogen PSA unit to form the high-pressure hydrogen product stream and the hydrogen-depleted tail gas stream comprises separating the synthesis gas in the hydrogen PSA unit to form the high-pressure hydrogen product stream, the hydrogen-depleted tail gas stream, and a fuel gas stream, further comprising:
 passing the fuel gas stream to a process unit as fuel gas. 
 
     
     
         9 . The process of  claim 1  further comprising:
 chilling a process stream with the warmed chilling stream after chilling the working fluid stream. 
 
     
     
         10 . The process of  claim 9  wherein the process stream comprises the synthesis gas stream, a feed stream to a dehydration unit, a compressor discharge stream, or combinations thereof. 
     
     
         11 . The process of  claim 1  wherein the chilling stream comprises liquified natural gas, further comprising:
 passing the warmed chilling stream to the synthesis gas production zone after chilling the working fluid stream; or 
 passing the warmed chilling stream to a natural gas network after chilling the working fluid stream; or 
 both. 
 
     
     
         12 . The process of  claim 1  further comprising:
 compressing and drying the hydrogen-depleted tail gas stream to form a dried compressed tail gas stream; and 
 wherein chilling the hydrogen-depleted tail gas stream with the chilled working fluid stream comprises chilling the dried compressed tail gas stream with the chilled working fluid stream. 
 
     
     
         13 . The process of  claim 1  further comprising:
 removing at least a portion of the water from the synthesis gas stream before separating the synthesis gas in the hydrogen PSA unit. 
 
     
     
         14 . The process of  claim 1  wherein the first heat exchanger comprises a printed circuit heat exchanger, a shell and tube exchanger, a brazed aluminum exchanger, a spiral wound heat exchanger, or combinations thereof. 
     
     
         15 . An integrated process for hydrogen production and carbon dioxide recovery comprising:
 introducing a feed stream comprising hydrocarbons or a carbonaceous feedstock to a synthesis gas production zone comprising a syngas reactor to produce a synthesis gas stream comprising hydrogen, carbon dioxide, carbon monoxide, and methane;   separating the synthesis gas stream in a hydrogen pressure swing adsorption (PSA) unit to form a high-pressure hydrogen product stream enriched in hydrogen and a hydrogen-depleted tail gas stream;   compressing and drying the hydrogen-depleted tail gas stream to form a dried compressed tail gas stream;   chilling a working fluid stream with a chilling stream comprising liquefied natural gas, or liquid nitrogen, or liquid ammonia, or liquid hydrogen, or combinations thereof in a first heat exchanger forming a chilled working fluid stream and a warmed chilling stream;   chilling the dried compressed tail gas stream with the chilled working fluid stream in a main heat exchanger in a cryogenic carbon dioxide separation unit forming a chilled dried hydrogen-depleted tail gas stream and a warmed working fluid stream, and separating the chilled hydrogen-depleted tail gas stream into a carbon dioxide product stream comprising carbon dioxide, and an overhead stream;   passing the warmed working fluid stream to the first heat exchanger;   separating the overhead stream in an overhead separation unit to form a low-pressure carbon dioxide stream enriched in carbon dioxide and an off-gas stream enriched in hydrogen and at least one of carbon monoxide and methane; and   optionally recycling the low-pressure carbon dioxide stream to the cryogenic carbon dioxide separation unit.   
     
     
         16 . The process of  claim 15  wherein the working fluid stream comprises a hydrofluoroolefin, a hydrocarbon having 1 to 5 carbon atoms, or combinations thereof. 
     
     
         17 . The process of  claim 15  further comprising:
 separating the off-gas stream in a second overhead separation unit to form a second hydrogen product stream and a second off-gas stream enriched in at least one of carbon monoxide and methane; 
 optionally passing the second off-gas stream to the synthesis gas production zone; and 
 optionally passing at least a portion of the second hydrogen product stream to a process unit as fuel gas. 
 
     
     
         18 . The process of  claim 15  further comprising:
 chilling a process stream with the warmed chilling stream after chilling the working fluid stream wherein the process stream comprises the synthesis gas stream, a feed stream to a dehydration unit, a compressor discharge stream, or combinations thereof. 
 
     
     
         19 . The process of  claim 15  wherein the chilling stream comprises liquified natural gas, further comprising:
 passing the warmed chilling stream to the synthesis gas production zone after chilling the working fluid stream; or 
 passing the warmed chilling stream to a natural gas network after chilling a working fluid stream; or 
 both. 
 
     
     
         20 . The process of  claim 1  wherein the first heat exchanger comprises a printed circuit heat exchanger, a shell and tube exchanger, a brazed aluminum exchanger, a spiral wound heat exchanger, or combinations thereof.